1. Field of the Invention
The present invention relates to an apparatus and method for providing a Voice over Internet Protocol (VoIP) service in a wireless communication system. More particularly, the present invention relates to an apparatus and method for operating Discontinuous Reception (DRX) in a VoIP based wireless communication system.
2. Description of the Related Art
Voice over Internet Protocol (VoIP) services refer to services supporting a voice call in the form of packet data. That is, the VoIP service is a technology proposed to provide voice services through a packet network such as an Internet Protocol (IP) network compared to a circuit switched network such as a Public Switched Telephone Network (PSTN).
In the VoIP service, an overhead caused by control and feedback information can increase in proportion to the number of service users. Accordingly, to reduce the overhead of the control and feedback information, wireless communication systems providing VoIP services provide a semi-permanent resource allocation technique. The semi-permanent resource allocation technique is a technique for allocating semi-permanent resources to a Mobile Station (MS), to reduce an overhead caused by a physical control channel for resource allocation.
To reduce the power consumption of MSs, wireless communication systems provide a Discontinuous Reception (DRX) technique. The DRX technique is a technique for an MS to monitor a physical control channel only in a specific subframe, thereby being capable of reducing the power consumption of the MS. The MS using the DRX technique can advantageously reduce the power consumption of the MS while maintaining connectivity with a serving Base Station (BS).
VoIP based wireless communication systems can reduce overheads caused by control and feedback information and reduce the power consumption of MSs, using the semi-permanent resource allocation technique and the DRX technique. In this case, the MS can receive a physical control channel only during a slot corresponding to a DRX activity duration of the MS. Thus, a BS has to allocate semi-permanent resources only to the slot corresponding to the DRX activity duration of the MS.
As described above, in a case where a VoIP based wireless communication system uses a semi-permanent resource allocation scheme and a DRX technique, a BS allocates semi-permanent resources only to a slot corresponding to a DRX activity duration of an MS. That is, because semi-permanent resource allocation is restricted only to a DRX cycle, the BS has a problem that scheduling flexibility is deteriorated.
Also, because the BS allocates the semi-permanent resources only to the slot corresponding to the DRX activity duration, there may occur a phenomenon in which only the slot corresponding to the DRX activity duration runs short of resources.